SAS - Selection and Training. Part 1 of 3. The SAS was a unit of the British Army during World War II formed in 1941. They are the elite unit for which all other units are based. In these videos you'll see a number of techniques which were used to judge a candidates mental strength and physical stamina. These may or may not be accurate. However, they act as an example or representation of the trials and tribulations that the candidates must undergo in order to obtain their winged dagger.